Snap action toggle switch for high altitude use



Nov. 17, 1964 L. A. YESKE 3,157,760

SNAP ACTION TOGGLE SWITCH FOR HIGH ALTITUDE USE Filed May 22, 1963 inF/G/ INVENTOR.

Lou/ls A. Yeske BY MS affomeys United States Patent This inventionrelates to electric switches and, more particularly, tolever-operated'overcenter snap-action electric switches" adapted for useat low atmospheric pressures at high altitudes;

Electric switches which perform with complete satis- V faction at lowlevels or low altitudes have been found unsatisfactory for high altitudeoperation where the air is thin, the atmospheric pressure low and thetires incident to contact separation and engagement occur more readilyand frequently and are harder to'extinguish.

Switches'which perform satisfactorily over long periods of time and formany thousands of cycles under rated conditionsof'currentand' voltagefor sea leveloperation have been found to? fail with burnt or frozencontacts after a short period of usage at high altitudes such as 50,000feet or above.

switchesywhen'u'sedin aircraft; mustiiot only perform properly at highaltitudes, but also at groundlevel and pressure and at intermediatealtitudes and pressures. At all the diflierent altitudes, thetemperature, pressure and relative humidity" values diifer greatly andaffect the con tact arcing conditions and, hence, vary the life of theswitch.

lt'is anobjec't'of this inven'tion to providean'improved quick make andbreak electric switch capable of use at hignaltitudes, suchasSQOOOxfeetor' more, and also at level and intermediate altitudesand which has along life' under such operating conditions.

Another object of the invention is to provide a mounting' for a'thin'sheet m'et'al'movable contactblade on a swingabl'e swit'chingyoke toovercome the tendency of the contact to cut into the yoke and becomeloose. and uncertain in 'it'smo'veme'nt when moving between difierentswitch ositions;

Another object of the in'ventionis' to provide a mount ing fora'swin'gable switch yoke, particularly yokes having a fiberglassreinforcement'within a synthetic resin body, which mounting willovercome thetendency of the yoke to wear away its bearings.

Another objectflof' the invention is' toprovide a switch of theforegoing type having its parts made of materials whichtoethencooperate'to rblon 'the life of the switch under adverse"eondition's'of h'ighand low temperature, pressure and humidity;stichaeoccui' at high altitudes and at'sea'l'evel andinb'etweenl I gOther obj ectsa'nd'adyaiitages" of the invention willoccur as it isdescribediri'connectiofi'withthe accompanying drawing.

In the drawing:

FIG. 1 is a section view of a switch with the section being taken alongline I--I longitudinally adjacent one wall of the casing so as to showthe interior parts.

FIG. 2 is a plan view of the switch shown in FIG. 1 with the cover andhandle and spring removed.

FIG. 3 is a perspective view of the center contact of the switch shownin FIG. 1.

FIG. .4 is a perspective view of the end contact of the switch shown inPEG. 1 and an associated plate.

FIG. 5 is a perspective view of the yoke with the movable contactsattached thereto as used in the switch of FIG. 1.

Referring to the drawings, the switch parts are mounted in a switchhousing of generally rectangular shape 3,1517% Patented Nov. 17, 1964molded from insulating material, such as Glaskyd v (a glass reinforcedalkyd molding compound) which is hollowed out to receive fixed switchcontact members 20 and 60, a bridging contact 30 mounted on a swingableyoke 40 actuated by an'overcenter spring 445 and operating lever 50, allas will be more fully described with respect to their riovel det'ailshereinafter. [Herein use of an asterisk indicates the associated word isa Trade Mark name] The housing hasr'ecesses 14 at each of its fourcorners for fixed contact members 20 whose form is best shown in FIG. 4.Each fixed contact'is'stamped from thin sheet metal into U-shape withtwo wings 23, 25 joined by a central part 21 which, when the contact isinserted in the housing, lies parallel'to'the e'ndface of the housing10.

One of the wings comprises a contact 25 for engagement by a bridgingcontact 30 while the other wing 23 acts as a locating and'p'ositioning'part to hold the fixed contact member from laterallmovement in therecess 14';

From the top edge of thecontact' member, a tab 27 is bent at a rightangle inwardly of the housing with a space between the'inrier' edgethereof and the'wing' 23 to' receive an insulating barrier plate 18which extends inwardly fromthe end WaIl of the housing. The bottom edge.of. the plate 18' i's recei'ved in a recess in the floor of the housing;The plate 1'8 shields the interior operating parts of the switch fromarcs drawn during" contact separation. I

.Arc barrier plates 18 preferably are blanked from Teflon afiuoro-carbon resin reinforced by glass cloth having very high arcresistance, very high continuous service'temperature and low dielectricloss. But a glasscloth'reiniorced plate' ofan epoxy; melamine, siliconeor polyester resin may also'be used.

The switch as disclosed also has a center contact and terminal member"60 comprising a central portion 62. lying'along a'nd perpendicular tothefloor of the housing from which contact portions 64ai1'd 66 extendupwardly at opposite ends, and a terminal portion 68' extending downthrough the hem of the" housin For" bridging the center contact and oneend contact or'the'other, such as fidand 25 for example, the bridgingcontact memher'30 "is'mouhtedon a swingable U shaped yoke 40. Theyoke-ispreferably made from a sheet of glass-cloth reinforced'laminate,such a s an epoxy resin, but'a melamine, silicone, polyester orfluoro-carbon resin (such'as Tefl5n"*)may also beus'ed. U

The oke haseuhnisnsaz adaptedto pivot in opposite seats 1.2}for'fiidinthe upper ldngit'u'dinal side wallsof the housing 10; g g 7 Due to-theabrasivenature' of the glass reinforcing in the 'housingand'the' yoke,the trunnions tend to wear away toorapidry. Hence, lt'ios e cylin diicalelectrically insulatin'g'bearin'gs 43 are provided on the trunnions. Thebearin'g preferably is' made of nylon or some other similar material'ofself-lubricating nature suchas Lexan", a polycarbonate resin. Experiencehas shown that such bearings increase the life of the yoke very greatly,up to and beyond the requirements of commercial acceptability.

For swinging the yoke between its two positions, a

conventional coil compression overcenter spring 46 is seated at one endon a spring seat or lug 44 on the transverse portion of the yoke whileits other end is engaged with the inner end of an operating lever 50pivotally mounted in a boss or neck 52 upwardly extending from a metalcover plate 54 secured over the top of the housing with an insulatinggasket or plate between it and the housing to shield the plate 54 fromthe interior currentcarrying parts of the switch.

The bridging contact member 30 is mounted on the side arms and trunnionsof the yoke member and is stamped from thin sheet metal. The member 30has a body portion from which contact arms 31 and 33 extend at anoblique angle with respect to one another. Because the contact isstamped from thin sheet metal, it would tend to cut into the yoke andbecome loose and unreliable in its operation in a relatively short time.To overcome this difliculty, tabs 35, 37 are bent out at right anglesfrom the body of the contact on opposite sides of notches from oppositeupper and lower edges of the contact which respectively receive thetrunnions 42 and lugs 43.

The lugs extend outwardly from the side arms of the yoke at pointsspaced from the trunnions and adjacent the transverse portion of theyoke. These tabs, thus, engage the fiat side faces of the lugs and ofthe trunnions so that as pressure is exerted on the bridging contactmemher by the yoke as the yoke swings from one position to another, thepressure is against a flat surface instead of a sharp edge.

Switches made as above described of the materials as indicated overcomethe problems created when switches are used at high altitudes and lowatmospheric pressures and also at sea level and normal atmosphericpressures. By the provision of the novel mounting of the yoke as abovedescribed, the tendency of the yoke to wear away at its trunnions hasbeen overcome; while the tendency of the movable bridging contact to cutinto the yoke has also been overcome by the provision of flat surfaceabutment of the bridging contact member against the yoke. Likewise, theprovision of arc bafile plates of the disclosed materials and the casingof the disclosed material greatly reduce arcing. These details are ofgreat importance and are responsible for operation of the switch up tocommercial standards whereas previous materials and constructions havefailed and been found to be entirely unacceptable commercially.

Modifications within the scope of the invention will occur to thoseskilled in the art. Therefore, the invention is not limited to thespecific configuration and arrangement of parts as illustrated anddescribed.

What is claimed is:

1. In an electric switch for operation under extreme differences ofpressure and temperature as are encountered in jet aircraft operation,an overcenter mechanism comprising a yoke of insulating material havinga crank arm, an insulating casing supporting said yoke, an operatinglever and an overcenter spring between said lever and yoke for movingthe latter, a stamped sheet metal contact mounted on said crank arm,said contact having notches for reception of spaced parts of said crankarm, portions of said contact adjacent said notches being bent to lieflush against the surface of said yoke on opposite sides thereof toreceive the thrust of said yoke as it is moved from one position toanother by said overcenter spring 2. In an electric switch, acontact-moving arm of insulating material having a\crank portion and apivot portion, an insulating casing supporting said crank, means to movesaid arm from one position to another algout its pivot portion, astamped sheet metal contact member having notches therein to receivespaced portions of said contact-moving arm, portions of said contactmember adjacent said notches being bent to lie flush against the surfaceof said crank portion on opposite sides thereof to receive the thrust ofsaid contact-moving arm as it is moved from one position to another andavoid sharp edges of said contact member cutting into said contactmovingarm.

3. In an electric switch as claimed in claim 2, a cylindrical synthetictough plastic bearing member having selflubricating properties mountedon the pivot portion of said arm, and a molded insulating casing havinga seat receiving said bearing portion.

4. In an electric switch as claimed in claim 3 wherem the contact-movingarm and the casing contain glass reinforcing material and said bearingmember is nylon.

5. A sub-assembly for an electric switch comprising an insulationcontact-moving arm having a crank portion and a pivot portion, a thinstamped sheet metal contact member mounted on said arm, said contactmember having notches for reception of spaced parts of said crankportion, portions of said contact adjacent said notches being bent tolie flush against the surface of said arm on opposite sides thereof toreceive the thrust of said arm as it is moved from one position toanother, a cylindrical tough synthetic plastic bearing member havingself-lubr1- eating properties mounted on said pivot portion.

6. An electric switch as claimed in claim 2 wherein the insulatingcasing is formed of molded synthetic glass-reinforced plastic materialand has a narrow compartment the floor and one wall of which are formedby portions of said casing, the fixed contact member being in saidcompartment with its contacting portion lying alongside of one wall ofsaid casing, an arc bafile plate formed of blanked synthetic glass-clothreinforced plastic material and located on the opposite side of saidcontact member to form another wall of said compartment, the bridgingcontact member being engageable and disengageable with said fixedcontact within said compartment in proximity to said compartment wallsto promote are quenching.

7. In an electric switch for operation under extreme differences ofpressure and temperature such as are encountered in present day jetaircraft, an insulating base, a narrow compartment formed in said base,a fixed contact member in said compartment stamped from sheet metal andhaving a contact portion adjacent one wall of the compartment and an endportion, an insulating bafile plate forming another Wall of saidcompartment, said fixed contact having a lug bent inwardly of thecompartment at its top and a side plate portion extending inwardly fromthe end portion of said fixed contact spaced from said lug, the top edgeof said bafiie plate being received and held between said lug and sideplate portion.

References Cited in the file of this patent UNITED STATES PATENTS1,880,775 Butler et a1 Oct. 4, 1932 1,923,428 Engstrom Aug. 22, 19332,120,423 Bentley June 14, 1938 2,727,107 Hubbell Dec. 13, 19552,899,524 Smith Aug. 11, 1959 2,913,284 Zankl Nov, 17, 1959

1. IN AN ELECTRIC SWITCH FOR OPERATION UNDER EXTREME DIFFERENCES OFPRESSURE AND TEMPERATURE AS ARE ENCOUNTERED IN JET AIRCRAFT OPERATION,AN OVERCENTER MECHANISM COMPRISING A YOKE OF INSULATING MATERIAL HAVINGA CRANK ARM, AN INSULATING CASING SUPPORTING SAID YOKE, AN OPERATINGLEVER AND AN OVERCENTER SPRING BETWEEN SAID LEVER AND YOKE FOR MOVINGTHE LATTER, A STAMPED SHEET METAL CONTACT MOUNTED ON SAID CRANK ARM,SAID CONTACT HAVING NOTCHES FOR RECEPTION OF SPACED PARTS OF SIAD CRANKARM, PORTIONS OF SAID CONTACT ADJACENT SAID NOTCHES BEING BENT TO LIEFLUSH AGAINST THE SURFACE OF SAID YOKE ON OPPOSITE SIDES THEREOF TORECEIVE THE THRUST OF SAID YOKE AS IT IS MOVED FROM ONE POSITION TOANOTHER BY SAID OVERCENTER SPRING.